1. Field of the Invention
The present invention relates to a radio communication terminal and, more particularly, to an active antenna system of a radio communication terminal that is capable of improving a speech quality of a radio communication terminal in an area where a radio environment is degraded and speech quality is adversely affected.
2. Background of the Related Art
In general, a radio communication allows a terminal and a base station to exchange information such as a signal, a code, a voice, a data or the like through a radio link, for which a radio communication terminal converts data into a radio signal by using a transmission circuit and transmits it through an antenna and extracts an effective data from a radio signal received by the antenna by using a reception circuit.
FIG. 1 illustrates a communication system of a radio communication terminal in accordance with the related art. As shown in FIG. 1, the related art communication system includes a radio communication terminal 1 having a passive antenna that transmits and receives an RF signal to and from an outside, and a base station 2 for transmitting the RF signal transmitted to and received from the radio communication terminal to a certain communication network through a cable network.
The radio communication terminal 1 forms a radio communication link by using a dipole antenna 3 which is inexpensive and does not assume a direction if a radio environment is favorable, or forms a radio communication link by using a directional antenna which has a direction toward the base station 2 where it is far away from the base station or the radio environment is not good. At this time, a communication path between the radio communication terminal 1 and the directional antenna 4 is implemented by a transmission line 5.
Generally, with its gain of some 2.5 dBi and omnidirectional radiation characteristics, the dipole antenna is designed to be adapted to the mobile communication. With such a low gain, the dipole antenna is not suitable for a fixed radio communication terminal. Thus, for the radio communication terminal, usually, it is connected to the directional antenna through the transmission line with a certain length and the directional antenna is installed outdoors or indoors to form a radio communication link. However, the directional antenna has a problem that its speech quality is degraded due to losses generated and attributed to the transmission line.
In the related art communication system of the radio communication terminal, since the dipole antenna and the directional antenna are passive type, a performance of the antenna is determined depending on a performance of the radio communication terminal. In addition, although the directional antenna has a better direction property than that of the dipole antenna, its speech quality is deteriorated due to the loss generated at the transmission line. Since the antenna characteristics are passive, there are limitations in improving the speech quality.